<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            height: 100px;
            background-color: aqua;
            /* 利用层叠特性，再次设置div的特性为行内元素 */
            display: inline; 
        }
        span{
            /* 把span改成块级元素，独占一行 */
            display: block;
        }
    </style>
</head>
<body>
    <div class="box">我是div元素</div>
    <span>我是span元素</span>
    <a href="#">百度一下</a>
</body>
</html>